83 



velvety growths composed of spores of the form shown in the illustra- 

 tion below. 



Though originally described as a distinct form from that found on 

 the tomato and other related plants, 

 more recent observers begin to doubt 

 whether it should be so regarded, but the 

 careful study necessary to settle the point 

 has not yet been made. In form the 

 fungus is certainly so much like the 

 similar fungus found on other solanace- 

 ous plants that it is difficult to point out 

 a real difference, provided the data are 

 derived from a good range of specimens 

 taken at various times of the year, and 

 from various parts of the host plants. 

 This will be partially evident from an ex- 



P j 1 f J. T 



animation ot the various, torms pictured 

 in these pages. 



Potatoes Suffering from this blight Fig. 95 Spores of the Macrosporium of 

 , -. !' .1 . i thepotato, the cause of the Leaf -wilt 



have come under notice in this btate or Leaf -curl of the potato, 



with considerable regularity for some 



years past, so that it seems to be a fair inference that the disease is not 

 uncommon ; still the grower's complaint is seldom great, and the 

 malady must be ranked among those of secondary importance, partly, 

 I doubt not, on account of the general dryness of the climate. 



In every instance it has been brought under notice at a date too 

 late for the profitable application of fungicides. The early application 

 of Bordeaux mixture will hold the disease in check. This has been 

 proved to be the case in other countries. Hence, if any grower suffers 

 regularly from this easily-recognisable disease, he may feel sure that 

 if he assumes from the time of planting that the disease will appear, 

 and sprays in anticipation of the attack, he will be adopting one of 

 the best known methods. 



Combined with this measure should be the careful destruction of all 

 infected material, not only of diseased potato plants, but also of 

 tomatoes, chillies, and, in fact, in my opinion, of any plants or parts 

 of plants known to suffer much from fungi of this class. 



The disease seems to start from the ground, or, at any rate, to enter 

 the base of the stalks first. This accounts for the peculiar curl of the 

 leaves, which results in part at least from poor functioning of the stalk. 

 This means, of course, that the fungus is already inside the plant, and 

 hence already beyond the reach of fungicides. The course of the 

 disease therefore indicates that care should be given to the ground as 

 the source of infection, and as it is a fair inference in the present state 

 of our knowledge that the disease arises from spores similar to those 

 produced on the leaves, we should pay particular heed to what becomes 

 of all such spores. They should be carefully destroyed, the best means 

 to this end being the destruction of all diseased plants, as recom- 

 mended above. 



